Despite its high cost, amorphous metal is gradually replacing electrical grade steel in transformer cores because it is a lower loss material. A wound core transformer can be made from amorphous metal by winding an amorphous metal sheet into a core, cutting one leg of the core, and forming the metal into a rectangular shape. The amorphous metal is then annealed, which converts it into a very brittle material. At this point, the core, except for the cut leg, may be protected by the application of a resinous coating. The coating prevents damage to the core and the escape of broken fragments of amorphous metal into the transformer oil where they might cause shorts. The cut leg is opened, coils are placed over other legs of the core, and the cut leg is closed and sealed. Final assembly is accomplished by placing the core with the coils mounted over its legs into a tank of oil where it is tested at high voltage.
The use of resinous coatings alone to protect the core has been found to be unsatisfactory because the coatings are not strong enough to withstand the stresses on the core, and they crack and fragment during use which can result in damage to the core. Cracking of the coating exposes the amorphous metal core to the oil in the transformer and permits fragments of amorphous metal to enter the transformer oil, possibly causing shorts.
It is the main object of this invention to protect amorphous metal transformer cores from damage, and to prevent pieces of the core from entering the transformer oil. It is a further object of this invention to provide protection that is inexpensive, easily applied, strong enough to resist damage during assembly and in operation, and is uniformly flat so that the coils can fit over the legs of the core.